Presently known magnetic heads or transducers incorporate magnetoresistive (MR) sensors for detecting magnetically recorded data. A magnetoresistive transducer can read information on a recording medium with much narrower track widths and yields better signal-to-noise ratio. Also, the output signal generated during the data reading process is independent of the traveling speed of the recording medium.
A typical magnetoresistive head includes a magnetoresistive sensor located between two magnetic shield layers. Disposed between the magnetoresistive sensor and the magnetic shield layers are insulating layers. During the data reading mode, the magnetic shields shunt away stray fields, thereby confining the magnetic flux that emanates from a record medium and which is sensed by the MR sensor. The changes in magnetic flux correspondingly vary the resistivity of the magnetoresistive sensor. A direct electric current passing through the magnetoresistive sensor generates a varying voltage which represents the data stored in the recording medium.
Implementations of MR read heads at a miniaturized scale encounter various practical problems. First, the MR sensor needs to be properly biased. The ferromagnetic layer in its natural state comprises a multiple number of magnetic domains separated by domain walls. These domain walls are highly unstable. During normal operations, the constant merging and splitting of the domain walls generate undesirable signal noise, commonly called Barkhausen noise, which degrades the performance of the magnetic head. To suppress the signal noise, hard magnetic bias layers are normally attached to the ferromagnetic layers for the purpose of aligning the magnetic domains in a single domain configuration. Furthermore, to position the ferromagnetic layer in the linear operation region, another bias, called transverse bias, needs to be provided to the ferromagnetic layer. A soft adjacent layer formed of a material with relatively high coercivity and minimal magnetoresistive response is disposed adjacent to and spaced from the ferromagnetic layer to provide the necessary transverse bias. Exchange coupling between antiferromagnetic (AFM) and ferromagnetic (FM) materials is also used to achieve such biases. In more recent recording devices, such as spin valve heads, the AFM/FM structure becomes the critical part of the device. An AFM/FM structure with superior magnetic properties will enhance devices such as spin valve heads, dual MR heads and dual spin valve heads. Also in inductive devices wherein lamination is used to reduce eddy current and extend high frequency performance, insulating AFM materials may be used as lamination spacers to strengthen signal domain structure in the pole pieces of the inductive head. This approach can significantly reduce signal noise and enhance high frequency performance.
For the above reasons, there is a need to provide a method of fabricating magnetic transducers and magnetic film structures that can interact with storage media having narrow recorded data tracks with high linear recording densities, yet sufficiently sensitive to sense only the data signals recorded on the magnetic media with undesirable signal noise screened out.